diff --git a/app/src/main/kotlin/jackall/overlaymulticounter/Const.kt b/app/src/main/kotlin/jackall/overlaymulticounter/Const.kt
index bc025e5..a66c556 100644
--- a/app/src/main/kotlin/jackall/overlaymulticounter/Const.kt
+++ b/app/src/main/kotlin/jackall/overlaymulticounter/Const.kt
@@ -12,6 +12,7 @@
         const val mainBannerUnitId = "ca-app-pub-6316747512041615/9128099610"
         const val overlayBannerUnitId = "ca-app-pub-6316747512041615/6310364583"
         const val interstitialUnitId = "ca-app-pub-6316747512041615/7926698582"
+        const val interstitialFrequency = 5
         const val develop = false
     }
 }
\ No newline at end of file
diff --git a/app/src/main/kotlin/jackall/overlaymulticounter/activity/MainActivity.kt b/app/src/main/kotlin/jackall/overlaymulticounter/activity/MainActivity.kt
index 0848df3..5ffa979 100644
--- a/app/src/main/kotlin/jackall/overlaymulticounter/activity/MainActivity.kt
+++ b/app/src/main/kotlin/jackall/overlaymulticounter/activity/MainActivity.kt
@@ -39,5 +39,6 @@
     override fun onStart() {
         super.onStart()
         AdUtil.startBannerAd(this, binding.root.main_banner_frame, AdSize.BANNER, Const.mainBannerUnitId)
+        AdUtil.startInterstitialAd(this)
     }
 }
diff --git a/app/src/main/kotlin/jackall/overlaymulticounter/utils/AdUtil.kt b/app/src/main/kotlin/jackall/overlaymulticounter/utils/AdUtil.kt
index 5f90e09..5bf2924 100644
--- a/app/src/main/kotlin/jackall/overlaymulticounter/utils/AdUtil.kt
+++ b/app/src/main/kotlin/jackall/overlaymulticounter/utils/AdUtil.kt
@@ -1,16 +1,19 @@
 package jackall.overlaymulticounter.utils
 
 import android.content.Context
+import android.util.Log
 import android.widget.FrameLayout
-import com.google.android.gms.ads.AdRequest
-import com.google.android.gms.ads.AdSize
-import com.google.android.gms.ads.AdView
+import com.google.android.gms.ads.*
+import jackall.overlaymulticounter.Const
+import jackall.overlaymulticounter.common.PreferenceKeys
+import jackall.overlaymulticounter.common.PreferenceNames
 
 /**
  * Created by matsumoto_k on 2017/11/10.
  */
 class AdUtil {
     companion object {
+        private var mySharedPref: MySharedPref? = null
         fun startBannerAd(context: Context, frameLayout: FrameLayout, adSize: AdSize, unitId: String) {
             val adBannerView = AdView(context)
             adBannerView.adSize = adSize
@@ -19,5 +22,49 @@
             val adBannerRequest = AdRequest.Builder().build()
             adBannerView.loadAd(adBannerRequest)
         }
+
+        fun startInterstitialAd(context: Context) {
+            if (mySharedPref == null) {
+                mySharedPref = MySharedPref(context, PreferenceNames.CONFIG)
+            }
+            val interstitialCount = (mySharedPref?.getValue(PreferenceKeys.interstitialCount, Int::class.java, 1) as Int)
+            if (interstitialCount == Const.interstitialFrequency) {
+                mySharedPref?.putValue(PreferenceKeys.interstitialCount, Int::class.java, 1)
+                val interstitialAd = InterstitialAd(context)
+                interstitialAd.adUnitId = Const.interstitialUnitId
+
+                interstitialAd.adListener = object : AdListener() {
+
+                    override fun onAdLoaded() {
+                        interstitialAd.show()
+                    }
+
+
+                    override fun onAdFailedToLoad(errorCode: Int) {
+                        val message = String.format("onAdFailedToLoad (%s)", getErrorReason(errorCode))
+                        Log.d("debug", message)
+                    }
+                }
+
+                val adRequest: AdRequest
+                adRequest = AdRequest.Builder().build()
+                interstitialAd.loadAd(adRequest)
+            } else {
+                mySharedPref?.putValue(PreferenceKeys.interstitialCount, Int::class.java, interstitialCount + 1)
+            }
+        }
+
+
+        // Gets a string error reason from an error code.
+        private fun getErrorReason(errorCode: Int): String {
+            var errorReason = ""
+            when (errorCode) {
+                AdRequest.ERROR_CODE_INTERNAL_ERROR -> errorReason = "ERROR_CODE_INTERNAL_ERROR"
+                AdRequest.ERROR_CODE_INVALID_REQUEST -> errorReason = "ERROR_CODE_INVALID_REQUEST"
+                AdRequest.ERROR_CODE_NETWORK_ERROR -> errorReason = "ERROR_CODE_NETWORK_ERROR"
+                AdRequest.ERROR_CODE_NO_FILL -> errorReason = "ERROR_CODE_NO_FILL"
+            }
+            return errorReason
+        }
     }
 }
\ No newline at end of file
diff --git a/app/src/main/kotlin/jackall/overlaymulticounter/viewmodel/MainViewModel.kt b/app/src/main/kotlin/jackall/overlaymulticounter/viewmodel/MainViewModel.kt
index f9f0b92..316ff6e 100644
--- a/app/src/main/kotlin/jackall/overlaymulticounter/viewmodel/MainViewModel.kt
+++ b/app/src/main/kotlin/jackall/overlaymulticounter/viewmodel/MainViewModel.kt
@@ -17,11 +17,12 @@
 import io.realm.OrderedRealmCollectionChangeListener
 import io.realm.RealmResults
 import jackall.overlaymulticounter.App
-import jackall.overlaymulticounter.adapter.CounterAdapter
 import jackall.overlaymulticounter.R
+import jackall.overlaymulticounter.adapter.CounterAdapter
 import jackall.overlaymulticounter.contract.CounterContract
 import jackall.overlaymulticounter.db.CounterRealmHelper
 import jackall.overlaymulticounter.service.MainService
+import jackall.overlaymulticounter.utils.AdUtil
 import jackall.overlaymulticounter.utils.RuntimePermissionUtil
 import jackall.overlaymulticounter.utils.ServiceUtil
 import jackall.overlaymulticounter.vo.Counter
@@ -55,8 +56,8 @@
     }
 
     fun onClickStartService(view: View) {
-        // TODO: RuntimePermissionの処理
         if (RuntimePermissionUtil.checkOverlayPermission(view.context)) {
+            AdUtil.startInterstitialAd(view.context)
             if (ServiceUtil.isMainServiceRunning(view.context)) {
                 val intent = Intent(view.context, MainService::class.java)
                 view.context.stopService(intent)